The present invention relates to a device and a method for manufacturing preforms of fiber reinforced plastic.
Today, glass fiber reinforced plastics (GFRP) and carbon reinforced plastics (CRP) are chosen increasingly often for use as the material for highly diverse applications. This is due to a growing demand for lightweight construction solutions. In the field of machine engineering and, in particular, aerotechnics and space engineering, and in the construction of wind power plants, highly stable and extremely lightweight solutions based on GFRP and CRP have become indispensible.
The advantageous properties of these materials have also proven valuable in automotive and aircraft construction, of course. Predictions call for an increasing use of GFRP and CRP components for production of very large quantities in automotive construction in particular.
In aircraft construction, which deals primarily with moving large masses, the performance of a product can be increased greatly by the use of lightweight construction solutions. For example, reducing weight can also help to minimize perpetual costs such as fuel costs.
The advantage of fiber reinforced plastics is their high specific strength and stiffness combined with very low density. This is a clear advantage over metallic materials. Due to the very low density of the fibers used, and given that density of the plastics used is even lower, these lightweight construction materials are clearly superior to classically used metallic materials in terms of weight.
The entire production of components made of fiber reinforced plastics is still highly manually oriented. This results in very high production costs, thereby rendering production of large quantities, let alone mass production, unaffordable at this time. Semi-automated or fully automated processes have become known only for components having very simple geometries. For example, pultrusion is used to manufacture straight shapes having a constant cross section. This is suitable for manufacturing plastic railings, plastic ladders, tent stakes, or bed frames, for example.
The curved structural components required in the aircraft and automobile industries in particular can only be produced manually at this time, which is an elaborate and tedious process. It is precisely such curved parts composed of fiber reinforced plastics, which are often required for aerodynamic reasons or due to greater stiffness, that are becoming increasingly significant in the field of automobile or aircraft construction.
To manufacture components having greater geometric complexity, so-called “integral components”, the desired structures composed of fiber semi-finished products such as rovings, wovens, non-wovens, fleeces, interwovens, or the like, are first draped into the desired shape. This takes place, for instance, by using a certain precut blank of the materials which are then draped around or in devices that are convex, concave, or have other three-dimensional shapes. Finally, the formed bodies, which are usually composed of a plurality of semi-finished products, are sewn together and impregnated with a plastic which sets to form the so-called matrix.
The disadvantages of this manufacturing method are, in particular, the small holes produced during sewing, which can negatively affect stability, for instance, since the seams can also destroy fibers.
Document EP 1 504 880 A makes known an automated process and a machine intended for use therefor, by way of which components having simpler geometric shapes, such as L, S, H, or hat shapes, can be manufactured out of prepregs in a semi-automated process. Slight curvatures can be created by tightening up the prepregs that are used in a special pressing mold during the process of manufacturing the component such that the component has a respective radius.
The disadvantage of such a method is that only very slight curvatures can be produced, and only prepregs but no other types of starting materials can be used. Prepregs are expensive and they must be covered with special sheets when stored, to prevent them from sticking together. These sheets must be removed, of course, before various layers are combined. This also complicates a continuous production of components. In addition, prepregs have a limited storage life before processing, and they must be stored in cool conditions.
Furthermore, the prepreg stack that was formed must be covered with other special sheets at the top and the bottom, to prevent them from sticking in the heated press.
To attain a desired curvature, these sheets must be prefabricated with precisely this curvature, which also requires a considerable amount of effort.
If structural components having greater complexity are required, for instance, they must be manufactured at this time as individual components having a simple geometry, which can then be combined to form the desired assembly using complex assembly processes. This production method results in very high costs, greater weight, and very long production times.